Chain tightener



Nov. 13, 1951 W' v COVERT ET AL 2,575,313

CHAIN TIGHTENER 'e 724ml E,

2 SHEETS-SHEET l GEO'QGE Q M/ z Y A E A .gg ,l vr n Filed May 7, 194e Nov. 13, 1951 w. v. cow-:RT ET AL 2,575,313.

CHAIN TIGHTENER Filed May fr, 194e 2 SHEETS-SHEET 2 l l u N F* I4 (d '(Q l :I L .-u- @L L |1| l Il n. 1 mul/V I Q Patented Nov. 13, 1951 CHAIN TIGHTENER William V. Covert and George G. Mize, Indianapolis, Ind., `assig-nors to Diamond Chain Company, Inc., Indianapolis, Ind., a corporation Vof Indiana Application May '7, 1946, `Serial No. 667,971

12 Claims.

This invention relates to devices for maintaining proper 'tension in power-transmitting chains, 'and in its more specific aspects to devices in which the desired tension is maintained by adjustment of a sprocket or other element over which one stretch of the chain runs. Because adjustments are required at Asuch infrequent intervals that the necessity for adjustment may be overlooked or postponed luntil the chain has become unduly loose and because of the danger of over-tightening, as Well as for other reasons, the maintenance of chain-tighteners in 'a proper state of adjustment frequently presents a problem. Automatic chain-tighteners have been proposed, but many of them "are unduly 'complicated while others involve danger of lovertightening the chain.

It is an obpject of our invention to produce a chain-tightener which, by automatically 'limiting the magnitude of chain-tightening effort, will prevent over-tightening of the chain. Another object of our invention is to produce a chain tightener which can'readily be operated as an incident to the performance of other maintenance operations on the machine Vor yapparatus with Which the chain tightener is associated. More specincally, it is our object to produce a simple and inexpensive chain-tightener which can be operated by pressure-lubricating apparatus employed to lubricate 'the machine with which the chain-tightener is associated and which, when so operated, will insure maintenance of proper adjustment.

In carryingr out our invention in its preferred form, We employ a chain-engaging element such as an idler sprocket mounted for movement in a chain-tightening direction; and to move such element in the chain-tightening direction, We employ a duid-pressure operated device adapted to be supplied with grease or other duid Athrough a conventional form of pressure lubricating fitting. Ratchet means of any suitable form v'may be employed to prevent movement ofthe chain-tightening element in a reverse direction. Associated with the fluid-pressure operated device we provide means for limiting the maximum uidpressure 'effective to move the element in the chain-tightening direction, thereby limiting to a predetermined amount the tension which can be introduced into the fchain by operation of the chain-tightener.

The accompanying drawing illustrates our 'invention: Fig. 1 is an end elevation and Fig. 2, a side elevation, both in partial section, illustrating one form oi chain tightener; `Fig. l3 is a side elevation of a modiied form of chain tightener; Fig. 4 'is a transverse section on the line 4 4 of Fig. 3; Fig. 5 is ian `e'n'd elevation, in partial section, of Still another modification; Fig. 6 is -a section on the line E---'S of Fig'. 5'; and Fig. 7 i's a vie'W 2 similar to Fig. 5 Ishowing a further modication.

The device illustrated in Figs. 1 and v2 embodies abase 11B rotatably supporting a shaft Il which 'extends through and in opposite'directions beyond the base. `Keyed orotherwise secured to the shaft I I on one side of the base I0 is a bearingmember I-2 which rotatably supports a chain-tightening idler-sprocket I3. The common axis of the bearing member :I2 and sprocket I3 is eccentric to the'axis of the shaft I I, so that by rotative adjustment ofthe shaft Il a chain I4 running over the idler sprocket I3 may be tightened.

Onthe opposite side of the-base I8 from the bearing member lzfthere is secured to the shaft II a ratchet I5 which cooperates with one or :more 4pawls I6 adapted to prevent rotation of the shaft I I Vin one direction. For advancing the shaft II in the opposite, or vchain-tightening, direction, 'We provide, `conveniently integral with the base HJ, a cylinder 2li which slidably receives a piston 2|. The cylinder '2t extends generally tangentially of the ratchet I5 and is provided `adjacent such ratchet with a slot 22 through which there projects `a pavvl 23. The pawl 23 is pivotally connected tothe piston, as indicated at 2'4, and is urged outwardly into engagement with the ratchet I5, as by means of a spring 2'5.

It'w'ill 'be obvious from the above description that by'oscillation of the piston 2l the ratchet I5, and With it the shaft II -and bearing member I2, can Vbe .advanced in ka chain-tightening directi'on. For the purpose 'of 'oscillating the piston 2l in the `cylinder 2i), We provide a 'compression spring 27 which, acting between one end of the cylinder 2l! and the piston 2l, biases the latter in one direction; Aand We arrange the lpiston 2| so that it may be forced in the opposite direction by fluid-pressure in the opposite 4end of the cylinder. As shown, the remote end of the cylinder is closed by a plug 28 in which there is mounted a lubricating `fitting -29 of the type adapted to receive fgrease Aunder pressure from a suitable source. The iitting V29, however, Vdiiiers from the conventional tting in that it lacks a check valve preventing the discharge of grease from the cylinder.

As will readily be understood, the base ID is intended for mounting on aframe or other structurein such a position that Vthe sprocket I3 will engagea stretch of the chain I4 which the device is to keep tight. Since the pawls l 6, as shown, are arranged to prevent counter-clockwise rotation of the shaft Ii, the device is so mounted in association with the chain vdrive that clockwise rotation of the shaft II Will produce tightening of the chain. When the chain is to be tightened, a grease gun is applied to the ntting 29 and grease under pressure is forced into the cylinder2ll to advance the piston therein. Inithis movement of the piston the p'avvl'23 engages the ratchet I5 to rock the shaft I I and bearing member I 2 in the chaintightening direction. When the gun is removed from the fitting 2B, the spring 21 will force the piston rearwardly. Any grease displaced from the cylinder 2Q by such rearward movement of the piston 2l will escape through the fitting 29. The pawls I6 co-operate with the ratchet I5 to prevent or limit reverse movement of the shaft I I.

In order to prevent the application of too great a chain-tightening effort, we employ a pressurerelief valve 3I which communicates with the interior of the cylinder 20 between the piston 2l and the plug 2B. Obviously, such a relief valve will limit the fluid pressure in the cylinder 2D and will thus limit to a maximum the chain-tightening effort. By properly coordinating the crosssectional area of the cylinder 23 and the eccentricity of the bearing member I2 with the relief pressure of the valve 3|, chain-tightening effort can be limited to any desired predetermined maximum.

The lubricating tting 29 is preferably of the type which is used throughout the machine with which the chain-tightener is associated. One such fitting, provided for lubrication of the idler sprocket I3, is indicated at 32. Ordinarily, a machine equipped with such fittings will be lubricated at predetermined intervals, and in the course of such lubrication the gun which is being used will be applied to the fitting 29 and grease forced into the cylinder 20. Movement of the piston 2| under the influence of fluid pressure will rotate the shaft I I in the chain-tightening direction until slack has been taken up. Thereafter tension in the chain will oppose further rotation of the shaft and will cause the fluid pressure in the cylinder 2B to increase to the maximum value permitted by the relief valve 3I. If the chain possessed sufficient slack to permit a tooth of the ratchet I to pass one of the pawls I 6, the operation just described will result in a permanent chain-tightening advance of the idler sprocket. On the other hand, if the chain originally possessed so little slack that it becomes taut and the relief valve 3I opens before a ratchet-tooth has passed one of the pawls IB, the idler sprocket will' drop back to its original position when the gun is removed from the fitting 29. Thus overtightening of the chain is prevented.

In the modification of the invention illustrated in Figs'. 3 and 4, the idler sprocket I3 is rotatably mounted upon a cylindrical bearing member 35. Such bearing member is provided with a chamber 36 which extends through it from one end to the other and which is closed at its ends by closure disks 31 and 33. The disks 31 and 38 have aligned openings which are eccentric with respect to the axis of the bearing member 35 and which are adapted to receive a stationary shaft 40 about which the bearing member swings in its chain-tightening movement.

Within the chamber 35, the shaft 40 is provided with a vane 4I which, in co-operation with the body of the shaft itself, divides the chamber 36 into two pockets designated respectively as A and B in Fig. 4. The chamber 3G has too opposite side walls both concentric with the axis 45, one on the radius of such shaft and the other on the radius on the outer edge of the vane 4I so as to maintain an effective seal between the chambers A and B as the bearing member 35 swings about the axis of the shaft.

The pocket A of the chamber 36 communicates through a radial passage 42 with an axial passage 43 extending to one end of the shaft and there Y the disk 3.

communicating with a lubricating tting 44. The other pocket B is provided with a vent opening, conveniently a hole 45 extending through In line with the pocket A, the disk 31 is also provided with a pressure-relief valve 3I.

When grease is forced through the fitting 44, it passes through the passages 43 and 42 into the chamber A, creating therein a pressure which tends Vto swing the bearing member 35 in a counter-clockwise direction about the axis of the shaft 4B to produce chain-tightening. The maximum extent of the chain-tightening will obviously be limited by the pressure-relief valve 3i which operates to limit fluid pressure in the chamber A to a predetermined maximum. In this device, since the pressure-operated element moves progressively in but one direction throughout the entire range of chain-tightening adjustment, it is not essential that the fitting 44 be valveless, as was the tting 29 in the device of Figs. l and 2.

To prevent chain-loosening movement of the bearing member 35, a stationary ratchet 48 may be secured to the shaft 40, or to a support 5I! in which such shaft is mounted, in position to cooperate with a pawl 49 suitably mounted on the disk 38.

The modification illustrated in Figs. 5 and 6 is similar to that shown in Figs. 1 and 2 in that it embodies a rock shaft I I rotatably mounted in a base II! and provided on one side of such base with a bearing member I2 for the idler-sprocket i3. In this instance, means for rotating the shaft vII to produce tightening of the chain embodies a pinion 55 which is secured to the shaft II and which meshes with a series of rack teeth 56 provided in one side of a piston 51 that is slidably mounted in a cylinder 58. As will be obvious, downward movement of the piston 51, such as will be created by the supply of uid under pressure to the upper end of the cylinder 58, will rotate the pinion 55 and shaft II rigid therewith to produce chain-tightening. Pawls 59, co-operating with the teeth of the pinion 55 will prevent rotation of the shaft I I in the opposite direction.

To eifect movement of the piston 51 in a chain- A tightening direction, the cylinder 53 is provided at one end with a lubricating fitting 60 through which grease under pressure may be forced into the cylinder. The fitting 6B, in this particular modification, is of the type known as a hydraulic shut-Gif fitting and embodies a valve which shuts oif at a predetermined pressure to stop further passage of grease. Although maximum chain-tightening eiort may be normally limited by a shut-off fitting, it is frequently desirable to provide the cylinder with a pressure-relief tting 3l in order to prevent the possibility of undue chain-tightening resulting from expansion of grease in the cylinder upon a rise in temperature.

It is frequently desirable to provide a chaintightener with a means operative to prevent chain-tightening movement which might result from the force of gravity, or from other relatively small chain-tightening efforts, coupled with the tendency of the chain to whip when operated at high speeds. One such means is shown in Figs. 2 and 6, Where We have illustrated a dished, resilient washer 55 which, in the assembled device, is axially distorted to bear frictionally against the support IB and the ratchet I5 (Fig. 2) or the pinion 55 (Fig. 6). Such a washer acts as a friction brake which, While not interfering with chain-tightening movement produced by the .relief tting i5.

grease gun, is capable of ypreventing the shaftV l I from rotating under theiniluence yof gravity vor other relatively small forces.

The effort required to eifect'retractionfof the Vpavvls I6 (Fig. l) or 59 (Fig. 5) when the shaft H is advanced obviously opposes any chaintightening movement. Byproperly co-ordinating the shape of the teeth-engaging paWl-portions `vvith the forces resiliently urging them toward engagement, the pawls themselves may be adapted 'to serve as means for preventing undesired. chain-tightening movement of the shaft l l.

kThe .device illustrated in Fig. '7 is a modificationof that shown in Figs. 5 and 6, in `which a .different means is employed to prevent `adventitious chain-tightening. In this instance, the end of the cylinder 58 remote from the grease-inlet tting `Eli is closed andprovided with a pressure- Further, the'piston`51 is provided with an axial passage '5l' extendingr through it and provided at the end remote from the inlet fitting `lill with a pressure-relief 'fitting 16.

The iitting 16 has a somewhat higher relief pressure than the fitting 75.

In the operation of the modification illustrated in Fig. 7, grease under pressure is supplied to the cylinder 58 through the fitting 6B. Fluid pressure in both ends of thecylinder 58 is thus increased, but the pressure in the remote end of the cylin- -der will be less than thatin the other end by the relief pressure of .thetting 76. Accordingly, the piston 51 will be urged in the chain-tightenvingdirection, any grease displaced from the re- '.mote end of the cylinder escaping through `the V'fitting l5. VIn this arrangement, grease under pressure is retained in the cylinder between the two'relief fittings 15 and 'i6 to oppose any tendency of the device to move in a chain-tightening direction except as a result of the vsupply of grease under pressure to the fitting 60.

vWhile the devices illustrated in Figs. 1 to 4 depend upon relief ttings `3| and the devices of Figs. 5 to 7 upon shut-off fittings 6D to limit maximum chain-tightening effort, it is toY be understood that any of the devices described, as Well as other devices Within the scope of our inventon, may employ either the pressure relief fitting, the shut-off tting, or any equivalent means for limiting to a predetermined maximum the fluid pressure which results in chain-tightening. Generally, the pressure relief type of tting is preferable where grease or other fluid is supplied at relatively low pressures, as by a manually operated gun, While the shut-01T type of fitting is desirable Where the actuating fluid is supplied at relatively high pressure, as byfa poweroperated device. Some power-operated, greasesupplying devices are capable of discharging grease under high pressure and at such a rate that theordinary pressure-relief tting 3l alone would be incapable of preventing the pressure within the fluid cylinder from rising above the desired maximum; and it is for that reason that the shut-01T type of fitting is preferred when the chain tightener is to be supplied with iiuid from i a power-operated source.

Whether the means employed to limit maximum duid pressure takes the form of the shutoff fitting 6e or the pressure-relief fitting 3l all the devices illustrated, as well as other devices Within the Yscope of 'our invention, operate to prevent the existence of a chain-tightening effort greater than a predetermined maximum. As the devices are all adapted for operation by pressure lubricating apparatus such as is used in idler.

Vlubricating other parts of vthe .machine with which the tightener is associated, it Will al- :ing which is angularly adjustable about an axis Yeccentric to the idler-axis, it is to be understood that the chain-engaging element need not be affsprocket, or even that it be rotatable. If the chain-engaging element of the 'tightener is a sprocket, it is not essential that it be a mere Neither is it essential that the support .for'the chain-engaging element or the tightener Nbezangularly adjustable in effecting chain-tightening;v as such support can be mounted for movenient oi any character which will result in changing the length of the chains path.

`We claim as our invention:

l. In a chain-tightener, a sprocket, a bearing member on which said sprocket is rotatably mounted, a support from which said member is supported'for adjustment about an axis eccentric to the sprocket axis, an actuating member for adjustingsaid bearing member in a chain-tightening direction/means for preventing movement 'of said bearing member in the opposite direction, hydraulic means actuatable by uid under pressure for applying to said actuating member a -force tending to move it to cause chain-tightening adjustment of said bearing member, said lhydraulic means being normally free rom uuid pressure and inoperative` to produce vcl'iain-tightening adjustment of said bearing member, a fitting adapted for temporary .connection to a lubricant gun and .communicating .with said hy- .member ion.. which said sprocket is rotatably ,.mounted,.a support from .which said member is vsupported for adjustment about an axis eccentric to the sprocket axis, an actuating member for adjusting saidbearing member in a chain-tightening direction, hydraulic means actuatable by fluid under pressure for applying to said actuating member a force tending to move it to cause chain-tightening adjustment of said bearing member, said hydraulicmeans being normally free frornfluid pressure and inoperative to produce chain-tightening adjustment of said bearing member, a iitting adapted for temporary connection to a lubricant gun and communicating With said hydraulic means to permit the supply or uid under pressure thereto from such gun, and .a valve for limiting to a predetermined maximum the pressure of fluidactuating said Yhydraulic means.

3- .In a .chain-tightener, .a chain-engagingelement, .a .support therefor., said support being movable to advance sai-d element in a chaintightening direction, means for limiting movement of said support in the opposite direction,

' hydraulic means actuatable by a iiuid under pressure for applying to said` support a `force urging it in the chain-tightening direction, said hydraulic means being normally free from fluid pressure and inoperative to produce chain-tightening adjustment of said support, a fitting adapted for temporary connection to a lubricant gun and communicating With said hydraulic means to permit the supply of fluid under pressure thereto from such gun, and a valve for limiting to a predetermined maximum the pressure of fluid actuating said hydraulic means.

4. In a chain-tightener, a chain-engaging element. a support therefor, said support being movable to advance said element in a chaintightening direction, hydraulic means actuatable by a uid under pressure for applying to said support a force urging it in the chain-tightening direction, said hydraulic means being normally free from fluid pressure and inoperative to produce chain-tightening adjustment of said support, a fitting adapted for temporary connection to a lubricant gun and communicating with said hydraulic means to permit the supply of fluid under pressure thereto from such gun, and a valve for limiting to a predetermined maximum the pressure of fluid actuating said hydraulic means.

5. The invention set forth in claim 4 with the addition that said hydraulic means includes an expansible chamber having an inlet passage for the admission of fluid under pressure, said pressure-limiting device comprising a' pressurerelief valve for said chamber.

6. The invention set forth in claim 4 with the addition that said hydraulic means includes an expansible chamber having an inlet passage for the admission of fluid under pressure, said pressure-limiting device comprising a pressureresponsive valve associated With said inlet passage and adapted to close when the pressure in said chamber attains a predetermined maximum.

7. In a chain-tightener, a sprocket, a bearing member on which said sprocket is rotatably mounted, a support from which said member is supported for adjustment about an axis eccentric to the sprocket axis, a pinion rigid With said bearing member, a stationary cylinder, a rod slidable Within said cylinder and having rack-teeth engaging said pinion, said cylinder having an inlet passage for admitting fluid under pressure to cause said rod to move and rotate said bearing member in a chain-tightening direction, and pressure-responsive valve means for closing said passage when the pressure within said cylinder attains a predetermined maximum.

8. The invention set forth in claim 7 with the addition of a pressure-relief valve for said cylinder.

9. In a chain-tightener, a sprocket, a bearing member on which said sprocket is rotatably mounted, a support from which said member is supported for adjustment about an axis eccentric to the sprocket axis, a pinion rigid with said bearing member, a stationary cylinder, a rod slidable Within said cylinder and having rackteeth engaging said pinion, said cylinder having an inlet passage for admitting fluid under pressure to cause said rod to move and rotate said bearing member in a chain-tightening direction, said cylinder being normally free from fluid pressure and inoperative to produce chain-tightening movement of said rod, a fitting adapted for temporary connection toa lubricant gun and communicating With said cylinder to permit the supply of fluid under pressure thereto from such gun, and a pressure-relief valve for limiting to a predetermined maximum the fluid pressure existing in said cylinder.

l0. In a chain-tightener, a sprocket, a bearing member on which said sprocket is rotatably mounted, a support from which said member is supported for adjustment about an axis eccentric to the sprocket axis, a pinion rigid with said bearing member, a stationary cylinder, a rod slidable Within said cylinder and having rack-teeth engaging said pinion, said cylinder having an inlet passage for admitting fluid under pressure to cause said rod to move and rotate said bearing member in a chain-tightening direction, means for limiting rotation of said bearing member in the reverse direction, said cylinder being normally free from fluid pressure and inoperative to produce chain-tightening movement of said rod, a fitting adapted for temporary connection to a lubricant gun and communicating with said cylinder to permit the supply of fluid under pressure thereto from such gun, and a pressurerelief valve for limiting to a predetermined maximum the fluid pressure existing in said cylinder.

11. In a chain-tightener, a rotatable chain-engaging element, a support therefor, said support being movable to advance said element in a chain-tightening direction, hydraulic means actuatable by a fluid under pressure for applying to said support a force urging it in the chaintightening direction, said hydraulic means being normally free from fluid pressure and inoperative to produce chain-tightening adjustment of said support, a fitting adapted for temporary connection to a lubricant gun and communicating with said hydraulic means to permit the supply of iiuid under pressurethereto from such gun, and a valve for limiting to a predetermined maximum the pressure of fluid actuating said hydraulic means.

i2. In a chain-tightener, a rotatable chain-engaging element, a support therefor, said support having a lubricant-passage for conveying lubricant to the interengaging faces of said element and support and being movable to advance said element in a chain-tightening direction, hydraulic means actuatable by a iiuid under pressure for applying to said support a force urging it in the chain-tightening direction, said hydraulic means being normally free from fluid pressure,

- and ttings respectively communicating with said passage and hydraulic means, said ttings having similar provisions adapting them for connection alternatively to a lubricant gun.

WILLIAM V. COVERT. GEORGE G. MIZE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 708,332 Ennor Sept. 2, 1902 2,002,081 Dow May 21, 1935 2,051,488 Kottlowski et a1. Aug. 18, 1936 2,258,465 Mullaney Oct. 7, 1941 

